Thermoplastic resins can have an excellent balance of physical properties and excellent moldability, and can be a substitute for glass or metal due to their low specific gravity. Accordingly, thermoplastic resins are widely used for various products such as automobile parts, electrical/electronic appliances, and the like.
Polycarbonate resin is an engineering plastic having excellent mechanical strength, heat resistance, transparency, weather resistance, flame resistance and the like. Accordingly, polycarbonate resin is used widely for electrical/electronic appliances, automobile parts, building materials and the like. Polycarbonate resin can also be a substitute for glass in applications demanding both transparency and impact resistance such as lens. However, polycarbonate resin has poor scratch resistance.
In contrast, polymethylmethacrylate (PMMA) resin has good transparency, weatherability, mechanical strength, surface gloss, adhesive strength, and excellent scratch resistance. It can be difficult, however, to impart impact resistance and flame retardancy to a PMMA resin.
An acrylic resin such as polymethylmethacrylate can be alloyed with polycarbonate resin to provide a thermoplastic resin composition with good scratch resistance. However, it can be difficult to obtain high transparency and colorability due to the difference between the refractive indices of the polycarbonate resin and the acrylic resin.
Korean Patent Publication Laid-open No. 2004-0079118 discloses a method of lowering the molecular weight of polycarbonate during a kneading process using metal stearic acid ester in order to improve the compatibility between a polycarbonate resin and a methacrylate resin. However, the blend of the polycarbonate and the methacrylate resin has significantly reduced mechanical properties.
U.S. Pat. No. 4,287,315 discloses a methacrylate resin with good impact strength by adding an ethylene-vinyl acetate rubber to a blend of polycarbonate and methacrylate resin. The resin blend, however, has low transparency.